Measuring static yield stress of electrorheological fluids using the slotted plate device |
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Authors: | Young Dae Kim Daniel De Kee |
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Institution: | (1) Department of Chemical and Biomolecular Engineering and Tulane Institute for Macromolecular Engineering and Science (TIMES), Tulane University, New Orleans, LA 70118, USA;(2) Faculty of Applied Chemistry, Chonnam National University, Kwangju, 500-757, South Korea |
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Abstract: | An electrorheological (ER) response is defined as the dramatic change in rheological properties of a suspension of small particles
due to the application of a large electric field transverse to the direction of flow. ER fluids are typically composed of
nonconducting or semiconducting particles dispersed in a nonconducting continuous phase. A sufficiently large electric field
will cause ER fluids to solidify, giving rising to a yield stress. Many applications in torque and stress transfer devices
were proposed employing the reversible yielding behavior of ER fluids. Successful applications depend on a large yield stress
of ER fluids and therefore accurate measurements of the yield stress of ER fluids are required. Reported experimental yield
stresses of ER fluids have been dynamic yield stresses obtained by extrapolating the shear stress–shear rate data to zero-shear
rate. It would be very helpful to the understanding of ER behaviors and the applications of ER fluids to be able to measure
the static yield stress of ER fluids accurately. The slotted plate technique has been shown to be a successful method to determine
the static yield stress of suspensions. The values obtained via the slotted plate method are static yield stress as the platform
is designed for extremely low-speed motion. In this study, we modified the slotted plate device for the application of large
electric fields and measured the static yield stress of TiO2 ER fluids under various electric fields. The measured static yield stress values are also compared with the static yield
stress values from a commercial rheometer. |
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Keywords: | Slotted plate device Yield stress Electrorheology Suspension |
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